Mushroom, Edible Mushroom

Introduction Mushroom

To this day, the origin of mushrooms has not been definitely clarified. It is supposed that they share their ancestry with the algae and protozoa. The earliest fossilized finds stem from approximately 300 million years ago.

Appearance, taste, characteristics

Mushrooms can be divided into three different groups: saprophytes, parasites and symbionts. The saprophytes settle on dead organic matter; parasites nest on living organisms, such as animals and plants; and the symbionts live in a cooperative relationship together with higher plants. Most edible mushrooms belong to the latter group. In this case the higher plants are deciduous and coniferous trees, in the vicinity of which the mushrooms grow and with which they form a symbiosis.

Common to all three groups is that they cannot produce chlorophyll and are not able to form their own organic substances out of sunlight and carbon dioxide by means of photosynthesis. They require substances that are already available for their nourishment and use those found in their given environment.

For this reason they are not considered botanically as plants. Biologists do not assign them to the plant kingdom or to the animal kingdom, but rather to their own kingdom known as the fungi. Based on their use as a vegetable, they are categorized here as vegetables.

A consensual combination of edible ascomycetes and basidiomycetes comprise the edible mushrooms. Usually they consist of a stem and a cap. The cap, on the underside of which are gills or tubules, carries the spores that are responsible for propragation. The function of the stem is to let the cap rise up as far as possible, in order that the spores are caught by the wind and carried further.

According to the shape of the mushroom and the location of the spores, we differentiate between cap, tree, ball, tongue, shrub, funnel and basin-shaped mushrooms. The cap-shaped have already been described, being the classical mushroom form known to all. Chanterelles are an example of the funnel-shaped mushrooms, and edible morels belong to the tree-shaped mushrooms.

Only the fruit or the receptacle of the mushroom is eaten, the part that grows above ground. In the ground itself the mushroom continues to grow and forms a web of hyphae. This can grow to several metres and is visible only under the microscope; it is called the mycelium.

The cultivation of some edible mushrooms began because people wanted to eat mushrooms out of season. At the beginning only the cultivation of white button mushrooms was successful, but improved technologies later made it possible to cultivate oyster and shiitake mushrooms, as well as several others.

Some of the important mushroom varieties are dealt with in more detail in the chapter on vegetables. There you can read more about white button mushrooms, truffles, oyster mushrooms and shiitake mushrooms.

Ingredients

Mushrooms in general can contribute to a good supply of vitamin D and some of the B vitamins. White button mushrooms, boletus and truffles contain more protein than other varieties, but they all supply essential amino acids. In addition to chitin, other unusable carbohydrates make mushrooms rather difficult to digest.

100 g contain:

Mushrooms,
fresh

Mushrooms,
cooked

Mushrooms,
tinned

Forest
mushrooms

Energy (kcal)

15

15

8,6

15

Water (g)

93

93

96

88

Protein (g)

2,7

2,7

1,6

2,1

Fat (g)

< 1

< 1

< 1

< 1

Carbohydrates (g)

< 1

< 1

< 1

< 1

Fibre (g)

2

2

1,2

7,6

Vitamin B1 (μg)

100

89

34

100

Vitamin B2 (μg)

440

391

201

400

Niacin (NE) (mg)

5,6

5

2,6

5,5

Pantothenic acid (mg)

2,1

1,9

< 1

2,5

Biotin (μg)

16

12

6

15

Vitamin D (μg)

1,9

2

1

2

Potassium (mg)

422

305

205

429

Phosphorous (mg)

123

123

64

121

Iron (mg)

1,2

1,1

< 1

< 1

Harmful substances

Undesirable fungi are moulds or those that trigger diseases in human beings, animals and plants. Heavy metals are more easily concentrated in mushrooms than in other plant foods. In addition, mushrooms are able to store radioactive caesium. However, this is a danger only with wild mushrooms, not with cultivated mushrooms.

With the exception of boletus, wild mushrooms should not be eaten raw, as they contain haemolysin, which destroys erythrocytes, or red blood cells. As cultivated mushrooms such as white button and oyster mushrooms contain no haemolysin, they can also be eaten raw.

Presumed effect on health

Researchers continue to discover ingredients in edible mushrooms that have antibiotic, immune-stimulating and cytostatic, i.e. inhibiting cell proliferation, effects and are also effective against viruses, high blood pressure and allergies, blood lipid concentrations and stomach and intestinal complaints.

In traditional Chinese medicine, mushrooms, above all the shiitake, have been used for many centuries. Today, scientists here are also studying their effects on health. The reduction of blood cholesterol is an effect that has already been proven. Treatment with mushroom preparations is known as mycotherapy.

Quality criteria, optimal storage conditions

When you are buying fresh mushrooms the following characteristics should be taken into consideration: They should look firm and succulent; larger mushrooms are usually more aromatic because they are riper. Do not buy any soft, dried out or speckled mushrooms, and pay attention to the stem end: if it is dry this is a sign that the mushrooms have already been in storage for a long period of time. In addition, there should be as few remainders of fir needles, leaves and earth as possible stuck to the mushrooms.

Due to their high water content, mushrooms spoil easily and must be stored in a cool, well-aired place. Do not pack them in a plastic bag, but rather in a paper bag; however, do not pack too many together, to avoid any bruising. In general, mushrooms should be eaten soon after they are harvested.

Form of consumption, use, processing, practical tips for preparation

Mushrooms have very varied effects. Man has put many of them to use, in both the food and the pharmaceutical industry. Thus mushrooms are used to produce antibiotics, but also as yeast to prepare various baked goods, beer, wine, yoghurt, etc.

They are available fresh in season and tinned, dried and deep-frozen out of season. In addition, pickled and salted mushrooms are produced.

The rule that mushrooms should not be heated up twice was known to our grandmothers. This statement is meanwhile obsolete, although the basic idea behind it is not wrong. Mushrooms belong to the highly perishable foods. The proteins they contain are easily decomposed by enzymes and micro-organisms characteristic to foods. If mushrooms that have been improperly prepared and stored are heated up again, these substances can lead to nausea, vomiting and diarrhoea.

Prepare your mushrooms therefore carefully; clean them thoroughly before you cook them to remove particles of dirt that contain such micro-organisms. Fry the mushrooms thoroughly as well; don't just steam them. If you then cool them quickly and store them in the refrigerator instead of leaving them at room temperature for several hours or even overnight, you can reheat them the next day without any hesitation. Just see to it that the mushrooms are heated well. Should you nevertheless have some misgivings, prepare only as many mushrooms as you can really consume. Incidentally, tinned and dried mushrooms can be reheated without any problem.

Miscellaneous

Some edible mushrooms are available pre-cultivated and can be grown privately at home. Thus there are specially prepared spawns suitable for growth on bales of straw, those that grow on wood, and others that grow in special small greenhouses no bigger than a hamster's cage. As in nature, the environment must meet certain criteria if optimal growth is to be achieved. Thus depending on the climate, some cultures are suited for growing outdoors, others for growing in damp, cool cellar rooms, and still others can grow on the windowsill at normal room temperature.

Tips for picking mushrooms

To protect the areas where mushrooms grow you should collect them only when you really intend to eat them. Always pick only as many mushrooms as you are really going to eat. To keep the mushrooms fresh for as long as possible, don't take a plastic bag into the woods, but rather an airy basket; as an alternative a cotton bag will also do. In a plastic bag the mushrooms will begin to sweat and will spoil more quickly.

It is not always easy to differentiate between poisonous and non-poisonous mushrooms. To avoid all risk, always carry an up-to-date book about mushrooms with you and pick only those that you are really convinced are non-toxic.

Many people use a knife to cut off mushrooms; it is better, however, to pull them out with a turn so that you can determine exactly what type of mushroom it is on the basis of the nodule and the sheath at the stem end. To protect the mycelium in the earth, cover the hole you have made with fir needles, leaves, or soil. Also leave gnawed, wet and old mushrooms where you find them in order to preserve the species; such mushrooms will in any case be sorted out and discarded later at home, either because they look unappetizing or because they no longer taste good.